Update CHANGELOG and history

Release 4.7.0 :gem:

Update skin count

Add plum skin to README

Add plum skin

Add placeholder to table

Update CHANGELOG and history

no message (#1319)

Update README

Update CHANGELOG, history, and README

Add neon skin

Update CHANGELOG and history

Update jekyll-toc with heading classes fix (#1337)

Update CHANGELOG and history

Aqua skin (#1336)

* Add new skin and update docs

* Better screenshots for aqua skin

Update CHANGELOG and history

Fix author profile link texts (#1328)

Refactor seo.html and support OpenGraph image overrides (#1321)

- Refactor seo.html include and add `page.header.og_image` override
- DRY up handling of page images (`page.header.image`, `page.header.overlay_image`, `page.header.teaser`, and `site.og_image`).
- Allow page images to be set with `header.og_image` page variable in YAML Front Matter as per feature request in #1316.
- Add sample posts for testing `og_image` override
- Set author bio as site OpenGraph default image
- Document `page.header.og_image` OpenGraph override
- Update CHANGELOG and history

Close #1316 

Merge branch 'master' of https://github.com/mmistakes/minimal-mistakes

# Conflicts:
#	docs/_docs/18-history.md

Adjust syntax highlighted code blocks padding

Rouge 2 adds `<div class="highlight"></div>` to markup which can introducing styling defects like extra padding.